Re: [Discuss-gnuradio] updating abstract classes

[Ilia Mirkin]

Quoting Charles Swiger <address@hidden>:

> On Wed, 2006-04-26 at 17:09 -0400, Ilia Mirkin wrote:
> > Quoting Charles Swiger <address@hidden>:
> > > ./atsc_equalizer.h:41: error: cannot declare field
> > > `atsc_equalizer::d_equalizer' to be of type `atsci_equalizer'
> > > ./atsc_equalizer.h:41: error:   because the following virtual functions
> > > are abstract:
> > > ./atsci_equalizer.h:159: error:  virtual void
> > > atsci_equalizer::filter_field_sync(const float*, float*, int, int, int)
> > > ./atsci_equalizer.h:140: error:  virtual void
> > > atsci_equalizer::filter_data_seg_sync(const float*, float*, int, int)
> >
> > I'm guessing that you don't find these messages particularly informative, so
> > here's what they mean:
> >
> > d_equalizer is of type atsci_equalizer; you're trying to instantiate 
> > one, but
> > atsci_equalizer is an abstract class because it doesn't have definitions for
> > these functions: filter_field_sync, filter_data_seq_sync. You can't
> > instantiate
> > abstract classes, so you must either define those functions or you must
> > specify
> > a more specific type for d_equalizer that can be instantiated.
> >
> > The reason you probably see segfaults with the pointer version is 
> > because you
> > never actually create an object that d_equalizer would point to (at least in
> > the code that you showed).
>
>
> Thanks, appreciate the explaination.
>
> Another modules, atsc_fs_checker, which also has some abstract
> classes DOES compile and run on meaningless streams w/o segfault
> so I can go by that (tomorrow!).
>
>
> Yeah - here's what I left out (arg!)
>
>  d_equalizer = equalizer;
>
>
> --Chuck

Yeah, so while atsci_equalizer doesn't implement these things,
atsci_equalizer_{lms,lms2,nop} do implement them. So you want something along
the lines of

atsci_equalizer *d_equalizer;

and somewhere in the code, do

d_equalizer = create_atsci_equalizer_nop() or something.

If d_equalizer points to a properly set up object, and ->filter() segfaults,
then there must be a bug in the filter() routine (or the inputs to it are
sufficiently wrong.)

 -Ilia